Air conditioning system for motor vehicles

ABSTRACT

Air conditioning (AC) system for motor vehicles comprising two fans connected in a series circuit whereby the first fan provides only a part of the air required for admission into the passenger compartment, and the remaining contribution to the desired quantity of air is provided by the second fan. Under normal operating conditions, where all openings such as windows, doors and sunroof (if any) are closed, both fans are independently regulated by a main controller device in such a manner that the air on the passenger compartment experiences a slight overpressure in order to permit the rapid entry and exit of air flow through the passenger compartment and a uniform air circulation therein. A manometer is included in the AC system to provide air pressure differential data (between the passenger compartment and the outside) to the main controller. The AC system also includes an AC program associated with a separate AC controller which are both subordinate to the main controller such that the excessive speed and related noise of each fan are greatly reduced. The independent control of each fan by the main controller results in ideal performance, even during the operating condition wherein the passenger compartment is partially opened (ie, where a window is rolled down).

FIELD

The invention relates to a method and apparatus for improving theoperation and performance of an automotive air conditioning system ofthe type having two fans connected in a series circuit, including afirst fan disposed in the dashboard area and a second fan disposedadjacent the rear vent openings of the automobile compartment. Moreparticularly, the invention relates to a method and apparatus forproviding an intelligent dual fan, serially connected air conditioningsystem which automatically adjusts to changing pressure conditionswithin the automobile chassis and whereby the noise generated from thefans is greatly reduced.

BACKGROUND

The typical air conditioning unit found in most automobiles comprises ofa heating and/or ventilating fan in the dashboard region and includes amanifold for directing hot or cold air out through various openingsabove and/or below the dashboard. Examples of air conditioning unitsproviding an additional second fan are disclosed and described in DE-OS33 04 575 and DE-OS 30 43 934.

The air conditioning unit described in DE-OS 33 04 575 places anadditional fan in the rear region Of the passenger compartment and ismounted to the existing rear vent opening located therein. Theadditional fan is provided to achieve a faster air exchange byexhausting interior air from the passenger compartment to the outsideambient atmosphere.

DE-OS 30 43 934 teaches to provide a second fan (in addition to a firstfan housed in a conventional manner in the dash board) behind the backpassenger seat to provide a uniform air circulation within the passengercompartment.

The addition of a second fan for the improvement of the operation ofautomotive air conditioning systems typically involves a trade off indriver (and passenger) comfort. For an air conditioning system employingtwo fans to perform adequately at higher vehicular speeds, the fans mustbe operated at their performance limits. This results in an undesirableincrease in the amount of fan noise perceived by the driver andpassengers. The undesirable fan noise is only compounded by the additionof a second fan in the rearward regions of the passenger compartment.

Therefore, there is a definite need in the art to provide a quiet airconditioning system having the advantages of quick air exchange betweenexterior and interior air and which provides uniform air circulation inthe passenger compartment. There is also a need in the art to provide animproved dual fan air conditioning system whereby the noise generated bythe fans is greatly reduced, and where the system is intelligent suchthat the fans recognize a sudden change in the passenger compartment airpressure (such as a sudden pressure drop in response to an openedwindow) and do not attempt to operate near their performance limits inorder to keep the passenger compartment pressurized.

THE INVENTION OBJECTS

It is among the objects of the present invention to provide a method andapparatus for operation of an automotive air conditioning system havinga second additional fan placed adjacent the rear vent openings of thepassenger compartment to provide for quick air exchange and uniform aircirculation;

It is another object of the present invention to provide a method andapparatus for an improved dual fan, serially connected automobile airconditioning system whereby the noise generated by the fans is greatlyreduced under all operating conditions;

It is another object of the present invention to provide a method andapparatus for an improved dual fan, serially connected automotive airconditioning system whereby an independent controller is provided tocontrol the output of the two fans by determining the pressuredifference between the interior passenger compartment and the outsideambient atmosphere;

It is still another object of the present invention to provide a methodand apparatus for an improved dual fan, serially connected automotiveair conditioning system which has an air conditioning program to specifythe air quantity and is subordinate to the controller so that control ofthe output performance of each fan is affected in response to changinginternal pressure conditions;

Still other objects will be evident from the specification, drawing andclaims in this case.

DRAWINGS

The invention is illustrated in more detail by reference to the drawingin which:

The FIGURE is a schematic of an automobile chassis showing the air flowand control logic of the air conditioning unit within the vehiclechassis.

SUMMARY

An air conditioning system for motor vehicles is provided having twofans serially connected and disposed within the vehicle so that thepassenger compartment experiences a slight overpressure as compared tothe outside ambient atmosphere and uniform air circulation and rapid airexchange is achieved. The dual fan air conditioning system comprises afirst fan disposed within a conventional air conditioning unit housingin the dashboard of the vehicle and a second fan disposed adjacent alateral chassis opening at the rearward-most portion of the trunkcompartment. Air is directed through and compressed into the passengercompartment by the first fan which results in a slightoverpressurization of the passenger compartment. This overpressurizationcauses the air to move in the rearward direction of the passengercompartment where it flows through a plurality of slits provided alongthe rear dash area adjacent the rear windshield. The air flow is thusdirected into the trunk compartment where it is drawn by suction throughthe second fan and exhausted to the outside ambient atmosphere.

Each fan is separately and independently controlled by a singlecontroller so that the overpressurized state of the passengercompartment or cabin pressure is maintained during all operating speedsof the vehicles (and hence the desired direction of airflow through thevehicle is achieved). The feature of separate and independent fan speedcontrol also results in the desired effect of significantly lowering thenoise level, as experienced by the driver and/or passengers, produced byeach fan, as neither fan is required to be operated at its performancelimit. In addition, any increase in the portion of the increased powerrequired for operation of a second fan is compensated in part by thefact that the two independently controlled fans may be designed foroverall smaller power output levels.

In a first operating condition, wherein the passenger compartment iscompletely sealed, ie, where all windows are rolled up, doors closed,and sunroof (if one is provided) is shut, the speed of each fan isindependently increased or decreased by the controller as the vehiclechanges speed during a driving trip.

We have found that increases of vehicle speed result in an increase inthe stagnation pressure within the vehicle compartment, thus causing thefan speed of a conventional single fan air conditioning unit to likewiseincrease. This results in the production of excess noise generated bythe fan operating at its performance maximum output. This is also thecase in conventional dual fan air conditioning systems wherein thesecond fan is merely utilized to permit faster air circulation or airexchange within the passenger compartment. Thus, as vehicle speedincreases, the speed of both fans likewise increases and an undesirablerise in vent noise generated by both fans is experienced.

In the present invention there is no appreciable rise in vent noisesince the fan speed of any one fan is never required to be operated nearits maximum performance output level as the second fan contributes tothe overall airflow through the passenger compartment.

A manometer is also provided to compare the internal passengercompartment air pressure with the air pressure of the outside ambientatmosphere. The manometer sends the actual value of this measurement tothe controller whereby the controller selects a desired value of airpressure (the desired value of the air pressure being slightly greaterthan the outside ambient air pressure) and uses this desired value toselect and adjust fan speed.

An underpressurization of the compartment may be due to the fact thatthe forward fan speed is too slow and the rear fan speed is too fast(i.e. the forward fan is not pushing or compressing enough air into thepassenger compartment at a rate faster than the air is vented off orsucked out of the passenger compartment by the second fan). Thecontroller senses this condition and alters the fan speed of each fanaccordingly.

In a second operating state wherein there is an opening in the passengercompartment to the outside ambient atmosphere (such as a rolled downwindow, open door, etc.) the controller deliberately overrides theprogram set by the air conditioning unit controller, thus preventing theforward fan from increasing its speed too much in order to try and matchthe demands of maintaining an overpressurized state within the passengercompartment. The rear fan is still permitted to run at a speedsufficient to exhaust air from the passenger compartment.

In an alternative embodiment, the first fan is disposed at the inlet tothe heating and ventilation housing adjacent the radiator tank while thesecond fan is disposed within a conventionally placed air conditioningunit in the dashboard. As in the first, preferred embodiment, the speedof each fan is separately controlled by a controller such that positiveair flow through the vehicle is achieved.

In both embodiments it is important to note that the placement of theadditional fan (ie, the rear fan in the trunk of the first embodimentand the forward fan in the engine compartment of the second embodiment)is placed within a sealed compartment (ie, the trunk of the firstembodiment and the engine compartment of the second embodiment) and thusdoes not contribute to the audible fan noise heard by the driver and/orpassengers. The other fan, being disposed within the air conditioningunit controller of the dashboard area is never operated at its maximumoutput level because of the balancing and offsetting properties of theadditional fan. Thus, this fan never generates a discernable increase inaudible vent noise because of the optimizing affect of the independentlycontrollable and serially connected second fan.

DETAILED DESCRIPTION OF THE BEST MODE

The following detailed description illustrates the invention by way ofexample, not by way of limitation of the principles of the invention.This description will clearly enable one skilled in the art to make anduse the invention, and describes several embodiments, adaptations,variations, alternatives and uses of the invention, including what wepresently believe is the best mode of carrying out the invention.

The FIGURE, a schematic view of a vehicle chassis, shows an airconditioning unit housing 3 disposed within the dashboard area to thevehicle chassis 1. The housing 3 includes a first fan 5 which is drivenby an electro-motor 7. In operation, outside air is sucked into thepassenger compartment 9 by the forward fan 5 where it is then compressedor directed through a manifold or distribution system (not shown) to thepassenger compartment 9.

A second fan 13 is provided in the lower rear portion of the trunkcompartment 11. The trunk compartment 11 is separate and sealed off fromthe passenger compartment 9. Thus, placement of the second fan in thismanner results in improved noise reduction as perceived by thepassengers in the rearward seat since the rear seat assembly acts as asound wall to noise generated by fan 13 within the trunk compartment 11.Air, which is directed from the passenger compartment, communicates withthe trunk compartment 11 by a plurality of slits 15 provided in theregion of the lower rear windshield edge. In operation, the passengercompartment 9 becomes overpressurized after the startup of the airconditioning system and this overpressurized state results in the flowof air in the direction of and through slits 15 into the trunkcompartment 11, where it is then drawn by suction through fan 13 so thatit can be exhausted to the ambient outside air via a rear or lateralchassis opening (not shown).

The overall system control comprises the air conditioning unitcontroller 19, separate controller 17, and manometer 21 for measuringthe difference between inside and outside air pressures. Associated withthe air conditioning unit controller 19 is an air conditioning programwhich initially instructs the system on the desired level of airconditioning (AC) required of the AC system as specified by the operator(driver or passenger).

As is shown in the FIGURE, controller 17 is the nerve center or brain ofthe control network for the present invention. Controller 17 directlycontrols the two fans 5 and 13 in response to the setting of the airconditioning unit controller 19 by the operator. Additional data that isto be employed by controller 17 in order to adjust the control settingsof the fans 5 and 13 includes the feedback pressure differentialinformation generated from manometer 21. Manometer 21 provides thecontroller 17 with continuous updated information on the status of theexisting air pressure differential between the interior passengercompartment 9 and the outside ambient atmosphere.

OPERATION OF THE AIR CONDITIONING SYSTEM

The following description of the operation of the air conditioningsystem of the present invention will be presented with reference to twooperating conditions.

Condition 1

The first operating condition assumes that all openings to the passengercompartment are sealed shut (ie, all windows are rolled up, all doorsare closed and the sunroof, if the vehicle includes one, is pulledshut). Some vehicles already have sensors for this condition. When theair conditioning unit is switched on, the air conditioning programwithin the air conditioning unit controller 19 decides the quantity ofair that is necessary for the system. This information is reported tothe controller 17 which then drives the motors of fans 5 and 13 inaccordance with the quantity of air selected by the air conditioningprogram. This results in the creation of slight overpressure within thepassenger compartment 9. The pressure difference between the passengercompartment 9 and the outside environment is then measured by themanometer 21 which measures and records the actual value of the pressuredifference and then reports this actual valve to the controller 17. Adesired value of the pressure is then stored in controller 17. Thedesired value is selected to be greater than the instantaneous outsidevalue by a set amount. Due to this offset, the passenger compartmentalways experiences a slight overpressure which facilitates the flow ofair from the passenger compartment through the trunk compartment 11 andto the outside via fan 13, but in no way is this slight overpressureunpleasant to those inside the passenger compartment 9. The offsetbetween the actual value of the pressure difference and the desiredvalue is sufficient to ensure that no air is sucked into the passengercompartment due to air leaks within the passenger compartment 9.

An overpressure in the passenger compartment 9 above the desired valuesignifies that either the forward fan 5 is forcing too much air into thepassenger compartment 9 or that rear fan 13 is sucking too little airfrom the trunk compartment 11. To correct for this situation, thecontroller 17 will either reduce the speed of fan 5 and/or increase thespeed of fan 13. The air conditioning program associated with the airconditioning unit controller 19 is subordinate to the controller 17 andthe controller 17 continuously monitors input from the air conditioningunit controller 19 and manometer 21 to correct for inadequate orunreasonable suggested pressure levels from the air conditioning programassociated with controller 19 and to specify the necessary corrected airthroughput for the entire system.

In the converse situation, where the pressure in the passengercompartment 9 falls below the desired value stored in the controller 17,then controller 17 either increases the speed of fan 5 and/or decreasesthe speed of fan 13 in response to the desired air throughput specifiedby the air conditioning program.

The above described control process is particularly suited for a drivingtrip wherein a number of speed changes of the vehicle are present. Theindependent control of the operating speed of fan 5 by the controller 17greatly reduces the unpleasantness experienced by the driver and/orpassengers from overpressurization or excessive fan noise associatedwith increases in vehicular speed. For example, in an automobile havinga conventional air conditioning system wherein the speed of theforwardly disposed fan is constant and the driving speed is increased,the pressure within the passenger compartment will also increase and,since the stagnation pressure increases. The noise generated by the fanwill likewise increase as it reaches its performance maximum output. Byadding a second, additional fan with independent speed control, neitherfan is pushed to its performance maximum as the independent control ofthe other fan eliminates the need for the full performance of a singlefan. Thus, the noise due to each fan is never excessive.

Condition 2

In a second operating condition, the operation of the air conditioningsystem is the same as before with the exception of a window, door, orsunroof being opened in the vehicle. In this condition, it is notpossible to generate the desired overpressure to the system. The airconditioning program of the controller 17 will recognize such a drasticdrop in internal air pressure and will accordingly instruct thecontroller 17 to correct the operation of the forward fan 5 so that itdoes not attempt to operate at its maximum speed. In other words, thecontroller 17 is not fooled by the fan speed levels suggested by the ACprogram. The forward fan 5 speed will be intentionally decreased by acertain amount so that it does not attempt to meet the desired set valueof the pressure level that was reported to the controller 17 by thepressure difference manometer 21.

The air conditioning program of the controller 19 is subordinate to thecontroller 17 so that the forward fan 5 is activated only in accordancewith the setting of this program. In this second condition, the rear fan13 is still permitted to run in order to ensure a better ventilation ofthe rear compartment.

It should be understood that various modifications within the scope ofthis invention can be made by one of ordinary skill in the art withoutdeparting from the spirit thereof. We therefore wish our invention to bedefined by the scope of the appended claims as broadly as the prior artwill permit, and in view of the specification if need be.

We claim:
 1. An air conditioning system for the climate control of thepassenger compartment of motor vehicle having at least two compartments,a forward compartment and a passenger compartment, comprising inoperative combination:a) a first fan for directing the flow of air intoand pressurizing said passenger compartment; b) a second fan forexhausting said air flow from said passenger compartment; and c) meansfor regulating the speed of both of said fans with respect to each otherwherein:i) said regulating means adjusts the workload and air throughputof each fan over the course of a driving trip in response to changes inpressure associated with variances in automobile velocity to reduceaudible fan noise and maintain a slight overpressure in said passengercompartment to promote rapid air exchange with the outside ambientatmosphere in a first, window-closed operating condition; and ii) saidregulating means reduces the workload and air throughput of each fan ina second, window-open operating condition.
 2. An air conditioning systemfor motor vehicles as in claim 1 wherein said fan regulating meansincludes:a) an air conditioning unit controller having means forcontrolling the air throughput within said passenger compartment inresponse to a climate input by a driver or passenger; b) means formeasuring the air pressure difference between said passenger compartmentrelative to the instantaneous value of said outside ambient atmosphere;c) a separate controller for the direct control of the speed of each ofsaid fans; and d) said separate fan speed controller including means forupdating and evaluating said air pressure differential informationreceived from said measuring means, wherein:i) the fan speed of each ofsaid fans is adjusted to match the specified air throughput of said airconditioning unit controller in said first window-closed operatingcondition; and ii) the fan speed of both of said fans is reduced to anair throughput level to a pre-determined substantially minimum airthroughput range in said second window open operating condition.
 3. Anair conditioning system for motor vehicles as in claim 2 wherein saidair conditioning unit controller is subordinate to said separate fanspeed controller to prevent excess fan speed due to sudden pressuredrops within said passenger compartment.
 4. An air conditioning systemfor motor vehicles as in claim 3 wherein said air pressure differentialmeasuring means includes a manometer.
 5. An air conditioning system formotor vehicles as in claim 3 wherein:a) said first fan is disposed inthe forward portion of said passenger compartment and is in aircommunication with at least one passenger compartment air intake duct toprovide forced air into said passenger compartment; and b) said secondfan is rearwardly disposed within said automobile in air communicationwith said passenger compartment having at least one vent opening toexhaust internal pressurized air from said passenger compartment to theambient atmosphere.
 6. An air conditioning system for motor vehicles asin claim 4 therein:a) said first fan is disposed in the forward portionof said passenger compartment and is in air communication with at leastone passenger compartment air intake duct to provide forced air intosaid passenger compartment; and b) said second fan is rearwardlydisposed within said automobile in air communication with said passengercompartment and having at least one vent opening to exhaust internalpressurized air from said passenger compartment to the ambientatmosphere.
 7. An air conditioning system for motor vehicles as in claim5 wherein:a) said motor vehicle includes a third compartment rearward ofsaid passenger compartment; b) said passenger compartment includes meansfor air communication with said third compartment; and c) said secondfan is disposed in said third compartment.
 8. An air conditioning systemfor motor vehicles as in claim 6 wherein:a) said motor vehicle includesa third compartment rearward of said passenger compartment; b) saidpassenger compartment includes means for air communication with saidthird compartment; and c) said second fan is disposed in said thirdcompartment.
 9. A method for improving the operation and performance ofan air conditioning system of a motor vehicle having at least 2compartments, including a forward compartment and a passengercompartment, said air conditioning system having dual fans connected ina circuit, said method comprising in operative sequence the steps of:a)providing a first fan for forcing into said passenger compartment atleast a portion of the total air throughput of said passengercompartment; b) providing a second fan for exhausting air from saidpassenger compartment of said automobile; c) providing means forcontrolling the air throughput of said passenger compartment; d)providing means for monitoring the pressure differential between saidpassenger compartment air pressure and the instantaneous outside ambientair pressure; and e) providing means for adjusting the speed of each ofsaid fans in relation to said pressure differential monitored during afirst window closed operating condition to produce said air throughputso that the workload of each fan is kept to minimum levels to reduceaudible fan noise while maintaining a slight overpressure in saidpassenger compartment to promote rapid air exchange with the outsideambient environment.
 10. A method for improving the operation andperformance of an air conditioning system for motor vehicles as in claim9 wherein said monitoring step includes the step of:a) providing meansfor downwardly adjusting the speed of each of said fans to apredetermined substantially nominal fan speed range in relation to saidpressure differential monitored during a second window open operatingcondition so that both of said fans do not run at their maximum outputlevels in an attempt to maintain a slight overpressure within saidpassenger compartment.